Enossal individual tooth implant and locking tool for use with such an implant
BACKGROUND OF THE INVENTION 
     The present invention is directed to an enossal implant, which is also known as an endosteal or endosseous implant. The implant of the present invention has a basic structure which is implanted in a jaw of the patient and threadably receives a spacer sleeve or element which, in turn, receives a metal implant post having fastening means for receiving an individual tooth, which is a snugly fitting, conditionally removable denture. 
     U.S. Pat. No. 4,793,808, whose disclosure is incorporated herein by reference thereto and which corresponds to European Published Application 0 216 031, discloses an enossal implant which has proven satisfactory in practice. However, when used as an individual tooth implant, difficulties are encountered in that it is not possible to reliably secure the denture against turning or twisting relative to the base structure unless the individual parts of the implant and the denture are bonded together. Such bonding leads to problems, for example in the case of a subsequent replacement of the denture or when the implant has possible become damaged due to breakage. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to providing an enossal individual implant which insures a reliable, simple and, if necessary, detachable securing of a denture against twisting with respect to the basic structure. 
     To accomplish these goals, the present invention is directed to an improvement in an enossal individual tooth implant which has a metal implant post with a head portion for receiving a removable denture with a snug fit, said implant post being threadably received in the inner bore of a spacer sleeve which, in turn, is threadably received in a bore of a basic structure mounted on a jaw of the patient. The improvements are that a spacer sleeve is formed of a base element or member having threads of a first pitch threadably received in threads of a bore of said basic structure, said base element on an upper end being provided with threads of a second pitch smaller than said first pitch, a ring element or nut-like spacer sleeve top being threadably received on the threads of the second pitch and having a shoulder for engaging an upper annular shoulder or face of said basic structure, upper end faces or surfaces of the base member or element and the ring element being provided with separate tool attachment means for simultaneously securing the base member against twisting as the ring element is rotated relative to the base member, said base member and ring element forming locking means for locking the spacer sleeve in the basic structure against turning and twisting. Thus, after the spacer sleeve base is inserted in the threaded bore of the basic structure, the ring element is rotated relative to the base element to engage the upper annular shoulder and to form a lock-nut arrangement to lock the spacer sleeve in position. 
     The tool attaching means provided on the end face of the spacer sleeve base can be diametrically directed attachment webs or projections which are received in a groove or slot formed in a tool for holding the base member in an anti-twisting condition. The tool attachment means provided on the end face of the ring element are at least two diametrically facing attachment slots or grooves for receiving a projecting blade of a tool. 
     In another embodiment of the invention, the inner bore of the base element, which receives the implant post, has a centering thread for attaching a locking tool in the vicinity of its upper edge. 
     The invention also proposes a locking tool for use with the individual tool implant of the inventive type, which tool has a base wrench complimentary to the tool attaching means provided on the end face of the base element and a second tool arrangement as a top wrench rotatable relative to the base wrench and complimentary to the tool attaching means provided on the end face of the ring element. 
     According to the invention, it is possible to have centering threads passing through the base wrench and top wrench in a concentric manner for insertion into centering threads of the spacer sleeve base. In the case of a locking tool of the above-mentioned type, the invention optionally proposes that the centering screw is operable by means of a knurled head. 
     Finally, in the case of a locking tool according to the invention, the base wrench and the top wrench can be provided with fastening levers which extend substantially at right angles to the axis of their relative rotation. 
     The invention is based o the finding that it is possible to secure or prevent rotation in the case of an individual tooth implant in that the spacer sleeve or element, the so-called insert, which is preferably made of titanium, is constructed in a two-part manner, as described hereinabove. The ring element or nut-like spacer sleeve top engaging on the shoulder or the upper annular edge of the basic structure is rotatable with respect to the spacer sleeve base element and is constructed in a screwable manner with respect to the spacer sleeve base element. As soon as the two-part spacer sleeve has been threaded into the basic structure, there is an easy relative rotation of the ring element with respect to the spacer sleeve bottom or base member, i.e. through an angle of 30°, so that the shoulder of the ring element is pressed with considerable force against the upper edge of the basic structure and the spacer sleeve base is locked by means of said press fit. This leads to a reliable individual tooth implant locking. 
     Other advantages and features of the invention will be readily apparent from the following description of the preferred embodiments, the drawings and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of the individual tooth implant with portions broken away to various degrees; 
     FIG. 2 is a top plan view of the device of FIG. 1 without the implant post; 
     FIG. 3 is a cross sectional view taken along the lines III--III of FIG. 2 with portions in elevation for purposes of illustration; 
     FIG. 4 is a side view with different portions broken away for purposes of illustration of an embodiment of the individual tooth implant in accordance with the present invention; and 
     FIG. 5 is a side view of a tool used for inserting the implants of the present invention with portions broken away for purposes of illustration. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The principles of the present invention are particularly useful when incorporated in a tooth implant, generally indicated at 8 in FIG. 1. The tooth implant 8 has a basic structure 10 of a known type, for example a titanium member coated with hydroxyl apatite. The base structure or member 10 has a bore 9 which has a threaded portion 11 into which is threaded a base element or member 12 of the spacer sleeve. The bore 9 above the threaded portion 11 has a counterbore portion 13 which is free of threads. A spacer sleeve top or ring element 14 is mounted on the base element 12. As illustrated, an upper portion of the base element 12 has threads 17 which coact with the threaded portion 11 to mount the base element in the basic structure 10. Above the threaded portion 17, the base element 12 has a second threaded portion 19 of a pitch which is smaller than the pitch of the portion 17. The top or ring 14 has threads 18 which are threaded onto the threaded portion 19 and has a lower shoulder 21 for engaging a shoulder 15 of the basic structure 10. The spacer sleeve formed by the base element 12 has a bore 23 which receives an implant post 16 of a mounting pin 20 on which the denture is rigidly connected. The mounting pin 20 has an annular groove 25 which receives an upper portion of the ring or top 14. 
     As illustrated in FIGS. 1, 2 and 3, the spacer sleeve base element 12 is provided with diametrically directed attachment webs or projections 22 which will be received in a slot of a tool to allow rotating of the base element 12 in the basic structure 10. Also, the upper surface of the ring element 14, which is received in the annular groove 25 of the mounting pin 20, is provided with four grooves or slots 24 which are displaced at an angle of 90° with respect to each other and together form a tool attaching means. 
     In the embodiment of the device shown in FIG. 4, the spacer element base 12&#39; has a threaded portion 26 which coacts with a threaded portion 29 of an implant post 16&#39;. The threaded portion 26 provides a centering thread arrangement. 
     In order to lock the base member 12 and its ring 14 in the basic structure 10, a tool, which is generally indicated at 40 in FIG. 5, is provided. The tool 40 has a shaft with centering threads 30 and concentrically arranged on the shaft is a basic wrench 32 in the form of a sleeve which terminates on a lower end with diametrically opposed slots 33, which receive the webs or projections 22 of the base element 12. Concentrically arranged on the sleeve forming the base wrench 32 is a top wrench 34 which is also a sleeve arrangement and has four projections 35 which are spaced apart by 90° around the circumference of the sleeve forming the wrench 34 and are complimentary to the four grooves 24 in the top or ring 14. 
     When performing an individual tooth implant locking, the following procedure is adopted. First, the ring 14 is assembled on the base element 12 and both parts which are made of titanium are then screwed in a conventional fashion into the basic structure 10. As soon as a shoulder 15 and 21 engage each other, an implant locking or rotation prevention is taken place in the following manner. First, the tool 40 is assembled with the end of the axially extending shaft received in the bore, such as 23, of the base element 12. If the base portion 12&#39; of FIG. 4 is present, then the shaft preferably has the centering threads 30 threaded into the thread 26. In this arrangement, this threading in or positioning will locate the tool so that the grooves 33 of the base wrench 32 receive the web or projections 22 and the top wrench 34 is positioned with its projections 35 received in the grooves 24. By means of small levers, preferably arranged to extend perpendicular to the axis of the shaft and the two wrenches, the base member 12 of the spacer sleeve is secured against rotation, but the top 14 can be turned with respect to the base member or element 12 to an angle of 30° or a half turn. Thus, in a manner due to the different types of threads, the ring element 14 of the spacer sleeve is locked with respect to the base element 12 as the shoulders 15 and 21 are forced into tight engagement with each other. 
     The construction of the tool attaching means on the spacer sleeve base portion 12 as an attachment web also has the advantage that after locking the base portion 12 and ring 14, the tool can be removed and the implant post 16 can then be inserted, either by a press fit or by screwing into the base element 12&#39; and is engaged with respect to the base portion 12 at a point below the attachment webs 22. In this way, the spacer sleeve can be unscrewed from the base structure 10, even following a breakage of the implant post 16 so that the individual tooth implant can be repaired without having to remove the basic structure 10 from the jaw. 
     Although various minor modifications may be suggested by those versed in the art, it should be understood that we wish to embody within the scope of the patent granted hereon all such modifications as reasonably and properly come within the scope of our contribution to the art.